When performing an image-guided procedure, a monitor displays for the user a model of a body part and a model of a medical tool, both registered in a reference coordinate system. The tool is being tracked relative to a reference unit rigidly attached to the body or fixed relative thereto. If the reference unit accidently moves, the model of the tool is displayed at an erroneous position and orientation relative to the model of the body part. When performing visor guided procedures, a model of the relevant body part is displayed to the user on the visor at a perspective corresponding to the position and orientation of the user relative to the relevant body part, such that the model appears to the user to be at the position and orientation of the body part. Specifically, in minimally invasive visor guided procedures, the user sees a representation of an internal body part (i.e., a model of the internal body part) where other body parts are perceived by the user to be transparent, and the user may perform the procedure without exposing the internal body part. To that end, the model is registered with the relevant body part (i.e., the position and orientation associated with the model corresponds to the position and orientation of the internal body part in a reference coordinate system). However, if the model and the internal body part fall out of registration, the user may be presented with erroneous information regarding to the position and orientation of the internal body part. One prior art technique for verifying registration during image-guided procedures employs intra-operative imaging (e.g. X-ray images or live fluoroscopy using a C-arm) presented on a monitor. The surgeon verifies that the position of the tool, as captured in the intra-operative images and presented in real-time on a monitor, corresponds to the position of the tool relative to the internal body part as it appears in the monitor of the image-guiding system, preferably from more than one perspective. Another prior art technique includes placing the tracked tool at selected locations on the body part that are visible by the surgeon and that also appear in the model of the body part, and confirming that the model of the tool is displayed on the monitor of the image-guiding system at the corresponding position on the model of the body part. Both techniques may interfere with the surgical workflow, distract the surgeon and lengthen the surgery, which may lead, among others, to an increased probability of infection.
P.C.T Application Publication 2014/139019 to Sela et al, entitled “System and Method for Dynamic Validation, Correction or Registration for Surgical Navigation” directs in one embodiment therein, to an overlay of a visualization of a tracked instrument and patient imaging information, on a video image provided during a procedure. According to the method directed to by Sela et al, any registration errors may be recognized by a user as a simple misalignment of the instrument visualization and the actual physical instrument seen on the video image.